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Articles published in 2012

The knot (pronounced not) is a unit of speed equal to one nautical mile (1.852 km) per hour, approximately 1.151 mph. There is no standard abbreviation but kn is commonly used; kt and NMPH are also seen. The knot is a non-SI unit accepted for use with the International System of Units (SI). Worldwide, the knot is used in meteorology, and in maritime and air navigation—for example, a vessel travelling at 1 knot along a meridian travels one minute of geographic latitude in one hour. Etymologically, the term knot derives from counting the number of knots in the line that unspooled from the reel of a chip log in a specific time.

A chip log, also called common log, ship log or just log, is a navigation tool used by mariners to estimate the speed of a vessel through water. The name of the unit knot, for nautical mile per hour, was derived from this method of measurement.

When the navigator wished to determine the speed of his vessel, a sailor dropped the log over the stern of the ship. The log would act as a drogue and remain roughly in place while the vessel moved away. The log-line was allowed to run out for a fixed period of time. The speed of the ship was indicated by the length of log-line passing over the stern during that time.

A salvage team will begin towing stranded oil tanker Pratibha Cauvery, which ran aground as Cyclone Nilam slammed into Chennai last Wednesday, from the city's shores on Thursday afternoon. A tug will start the operation to recover the ship around 3pm, when tides are expected to be high. The vessel lost anchor after being hit by huge waves and drifted towards Elliot's Beach, where it hit the shore. Six sailors drowned in an attempt to escape from the ship. The vessel later drifted north and is currently located around half a nautical mile from Marina Beach.Vijai Saxena, head of the naval architecture department at Pratibha Shipping Company, the vessel owner, said a ninemember team from maritime company Smit International, Singapore, has planned the salvage operation with data from the Indian Naval Hydrographic Department's tide table."The table predicts the waters that the ship is stranded in will be reach a height of 1.1 metres at 3pm on Monday," Saxena "If the high tide does not materialise as expected, the operation will be deferred to Friday, when the tide forecasts the water level at 1.03 metres at 4.55 pm."He said the team is taking into account various factors including wind direction and possible damage to the vessel while planning the operation. "The tug will tow the ship bowfirst towards the sea," he said."The salvage team will have to tow out the ship carefully to prevent further damage to the keel or propellers," said a senior official of the directorate-general of shipping. Once the ship is taken out to sea, divers will photograph the hull, keel and propellers to assess the extent of damage caused by the ship running aground, he added, Experts said the salvage team will face a major challenge in manoeuvring the ship out to sea while ensuring that it does not tilt and capsize, an outcome that would not only damage the vessel but also result in the possible leak of the heavy fuel on board.Officials said nearly 10,000 tons of ballast water will be drained out to make the vessel light. "It is already free of cargo. Reducing the ballast will make it easier for the vessel to float in high tide," an official said. Ballast water is used to stabilise vessels, especially large ships that carry cargo.The directorate-general of shipping official said the salvage team is confident that it will be able to extricate the ship with the tug Malaviya. Another tug sent by the directorategeneral of shipping in Mumbai is heading for Chennai to provide additional towing power if needed.